title: Site-specific acylation changes in the lipid A of Escherichia coli lpxL mutants grown at high temperatures.
abstract: LPS is a major component of the outer membrane of Gram-negative bacteria. The lipid A region of LPS mediates stimulation of the immune system. In E. coli, the gene (formerly htrB) codes for a late lauroyltransferase (LpxL) in lipid A biosynthesis. E. coli lpxL mutants have been described previously with impaired growth above 33°C in rich media. However, we were able to grow lpxL mutants at 30°C, 37°C and 42°C, and investigate their lipid A moieties to gain insight into changes and regulatory effects in lipid A biosynthesis. Multiple-stage mass spectrometry was used to decipher unusual lipid A structures produced by lpxL mutant bacteria at high temperatures that rescue the temperature-sensitive phenotype. At 37°C and 42°C, E. coli lpxL mutants appear to activate different acyltransferases or biosynthetic pathways that generate atypical penta- and hexaacyl lipid A structures by incorporating longer fatty acids, such as a secondary palmitoleic acid (2'-O-position, distal) and a secondary palmitic acid (2-O-position, proximal) respectively. However, we observed no changes in these structures through various growth curve stages. This study indicates that E. coli (lpxL) lipid A biosynthesis, and specifically the 'late' acylation of lipid A, is temperature dependent, thus suggesting a highly regulated process.
authors.affiliation: 1The Buck Institute for Research on Aging, Novato, CA, USA.
authors.forename: Birgit
authors.initials: B
authors.lastname: Schilling
authors.forename: Jason
authors.initials: J
authors.lastname: Hunt
authors.forename: Bradford W
authors.initials: BW
authors.lastname: Gibson
authors.forename: Michael A
authors.initials: MA
authors.lastname: Apicella
mesh_terms: D000215:Acylation; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D006358:Hot Temperature; D008050:Lipid A / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000302:isolation & purification; D009154:Mutation / Q000235:genetics / Q000502:physiology; D012329:RNA, Bacterial / Q000096:biosynthesis; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology
chemical_list: D008050:Lipid A; D008070:Lipopolysaccharides; D012329:RNA, Bacterial
keywords: Late acylation; lipopolysaccharide; lpxL; mass spectrometry; temperature regulation